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Trench Depth?!

I have read so many different things about how deep to bury the pipe I am seeking some guidance in this area. I live in central Oklahoma and from what I can find the frost depth is around 18 inches. I have read differing statements in that I need to trench to at least the frost line and that 8-12" is as deep as I need to go. Also, my main line is 1"

Please someone give me a certain answer on how deep to trench in my location!?

I did install my own sprinkler too, and learned some lessons, and some of them the hard way. I live in Texas and I don't have a frost line problem where I live, so take my comment about that for what it may be worth.

Your main line must absolutely be below the frost line, because it will always have water in it and its subject to freezing.

Put in a blowout fitting just after your shut off valve. This will let you blow air through from there through the rest of the main, backflow and through the valves, laterals, and sprinklers, I would not think need to be below the frost line as long as you winterize the system and blow out all of the water. Seems logical to me. No water, no bursted pipes. Then you don't have to worry too much about it. There are drains you can install, but I've no idea if they are trustworthy, especially over a period of years.

I just finished my own sprinkler a couple weeks ago. A couple of tips on the trenching.

Trench a bit deeper than what you think you might need to. Why? Because the trencher will leave a good bit of dirt in the bottom of the trench. If you want a trench 7 inches deep, like me, and you set the trencher to dig that deep, like I did, then you will have to remove about 2 inches of dirt from the bottom of the trench that the trencher left in there. -- A better idea would be --, if you want 7 inches from top of ground to bottom of the pipe, then I recommend to trench 9 or 10 inches and don't worry about shoveling out any dirt of the trench.

I think the pro's have a special sort of shovel to get dirt out of the trench bottom and do it, but I don't have one. Wish I did.

By the way, in case you don't know, a typical shovels is too big to get dirt back out of the trench if it isn't deep enough. You will be down on your hands and knees scooping it out with a spade or with your hands. Get knee pads. They help, but you still are gonna be hurting. Or maybe you can find one of those pro trench shovel things with a long handle that I heard about after it was too late.

Another thing too, you are also going to knock more than a few piles of dirt back into the trench while you are putting in the pipes and whatnot. If you have a shallow trench, you will have to get that dirt back out too. Again. I trenched about 1300 feet with the ditch witch. I was on my hands and knees for probably 500 feet with a garden spade and my bare hands getting that loose dirt back out of that dam trench. And I'm no spring chicken either.

One of my neighbors even thought I was stoned on LSD while watching me crawl around on my hands and knees digging up a trench with a garden spade and my hands, that I already had dug with a trencher!

Also if you are going to put more than one pipe in the same trench, then trench deeper still. I rented a ditch witch track trencher, (it was a bada$$ trencher too) ... and the trench it makes is only about 2 1/2 or 3 inches wide at the most. So multiple pipes (I installed 1" pipes everywhere) in the trench are not exactly side by side, they end up a little bit stacked. So consider the height of all the pipes in the same trench if that is what you plan to do.

To be honest, it is not any harder at all to fill up a 10 deep trench than a 6 deep trench.
It is much much much much much easier to put dirt back in a trench that is deep enough, than to get dirt out of a trench that is not.

All in all, there were times when I ask myself what in the hell was I thinking taking on this project at my age with zero experience installing one, but i survived (barely) but it was more than worth it ... and I could not be more proud of my sprinkler.

One more tip. Get those trenches filled back up as quick as possible. I didnt have any help to speak of, So I trenched 1300 feet all at once and so the trenches stayed open for a little over a week. If your soil is clay, it will dry out and crack and turn into what I can only describe as billions of small clods which resemble rocks and big clods of hard dried clay dirt. That was no fun. Get the dirt back in the trench before it dries out too much because it will be hell if you don't if you have clay soil like me.

Now that I have finished, except for a bit more clean up of the dirt around those dam trenches, I cannot even begin to also say how much more respect I have now for people who do this for a living.

As a sprinkler tech in Kansas, you need to install a blowout port. Have someone come blow the system out every fall (Oct to Nov) depending on weather. I would trench to a depth of 8 inches. That will allow the lines to be at a safe depth for future lawn maintainance. Have you considered renting a vibratory plow and pulling the pipe in? It's a bit harder to do, but allows for minimal scaring of the grass. You will see a small slice in the ground that will almost disappear when you drive the machine back over it. You only dig the connection holes, head holes, and valve boxes.

You can use the drains the previous poster mentioned, but I've found that over the years they clog with dirt and don't work any more. The proper way to install the drain involves digging a hole under the drain and filling back with gravel, as well as covering the drain with gravel. When winter hits, with clogged drains, your system breaks in multiple spots and large repair bills result. The other issues with drains is all of the piping has to be sloped to the drain.